I have no reference to cite from the world of academia; however I can share what helps me with utter fatigue include better movement, better sleep, and better nutrition. Those are my three pillars of life today.

The problem is what comes first, the chicken or the egg? My health impact the three and the three impact my health. The four are connected hand in hand.

I find, sometimes, pausing and then pushing through makes a difference. MPNs demand a pause sometimes.

Perhaps we must all contend with ups and downs, now much more profound with an MPN?

Dunno, I’m humble to admit

Dear Erik,

You asked a fundamental question.
I searched for answers, there are not many, but I could find a couple of studies that were more focused on what could explain fatigue in MPNs. The most likely causes identified were the bone marrow producing less blood cells (e.g., in MF), the aftermath of phlebotomy in PV (anemia), cytoreductive treatment itself and the chronic inflammation that is a staple in MPNs.
There are other speculations, but as correlation does not mean causation, they are only speculations.
I found the study below more adequate than others as it goes and looks for biomarkers, rather than just speculate patients might be anxious. Of course patients might have some anxiety, they have a chronic cancer that makes the future uncertain. Who wouldn't have anxiety in this situation?
This is the study:
http://dx.doi.org/10.1155/2015/284706
"Emerging data demonstrates clear relationships between individual MPN symptoms (fatigue, abdominal complaints, microvascular symptoms, and constitutional symptoms) and cytokines, particularly IL-1, IL-6, IL-8, and TNF-α."

I hope it will be useful to you.

Best regards,
Tatiana

Hi, Erik. Fatigue has been my number one symptom. I push myself to stay active meaning keeping my behind off the lounge chair. I try to eat healthy. I take a cannabis nighttime edible candy (it is legal here in Arizona) and that seems to help me get a better night sleep. I have excepted the fact that this is part of my life and it will probably get worse but I have faith and try to make the best of it. I hope you and your family are doing well, Jim.

Thanks Tatiana